KR20020057394A - The bias circuit of power amplifier in used mobile communication terminals - Google Patents

Abstract

PURPOSE: A power amplification bias circuit for a mobile communication terminal is provided to maintain a bias constantly without regard to temperature variation by using a transistor for performing a feedback of bias in a bias circuit. CONSTITUTION: A first transistor(Q1) performs a feedback of a bias permitted into a power amplifier. A second transistor(Q2) restricts bias variation in interlocking with the first transistor(Q1). A first power supply unit(V1) supplies a collector of the first transistor(Q1) and a base of the second transistor(Q2) with power. A second power supply unit(V2) supplies a collector of the second transistor(Q2) with power. A bias permitting tap(BI) permits the electrostatic bias into the power amplifier through the first transistor(Q1) and the second transistor(Q2). A third transistor(Q3) amplifies a signal in which the bias is permitted.

Description

The bias circuit of power amplifier in used mobile communication terminals

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplification bias circuit of a mobile communication terminal. In particular, a power amplification bias for improving a linearity of an amplifier by stabilizing a bias of a power amplifier that plays an important role in transmitting a signal of a terminal in a wireless interface. It is about a circuit.

With the expansion of the mobile communication market, the demand for mobile communication terminals and communication devices has reached a considerable amount, and there is a need for high performance and small size and light weight communication devices. In order to reduce the size of a mobile communication terminal, a high density integrated circuit has been manufactured. Accordingly, technical efforts for improving performance within a limited area of a communication device have continued.

In particular, a mobile communication terminal requires a terminal having a high reliability having a certain linearity regardless of the power level of an external input signal.

1 is a circuit diagram showing a power amplifier circuit for a mobile communication terminal according to the prior art, the transistor (Q) for amplifying the power of the signal, and the bias distribution resistors (R1, R2) for applying a bias voltage to the base of the transistor And a resistor (Rc) for controlling the power applied to the collector of the transistor, a resistor (Re) for protecting the transistor (Q), a collector and bias distribution resistor (R1, R2) of the transistor (Q). It consists of the power supply Vcc which supplies a voltage.

Referring to FIG. 1, an operation of a conventional power amplifier circuit for a conventional mobile communication terminal configured as described above is applied to an external signal, and a voltage is distributed through bias distribution resistors R1 and R2 according to a signal level. Voltage is applied to the base, and the power of the signal is amplified in the transistor.

However, in the conventional power amplification bias circuit for a mobile communication terminal, the bias is distributed through the bias distribution resistors R1 and R2 to apply the transistor Q bias. The variation of the base-emitter voltage Vbe of the transistor Q according to the change causes gain instability and phase distortion during signal power amplification, thereby affecting linearity. There is this.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and its object is to operate a power amplifier using a transistor that feeds back a bias circuit to a bias circuit used in signal power amplification, even when the temperature rises. The present invention provides a power amplification bias circuit for a mobile communication terminal that can maintain a constant bias to improve linearity of a terminal.

1 is a circuit diagram of a power amplification bias for a mobile communication terminal according to the prior art;

2 is a circuit diagram according to a first embodiment of the present invention;

3 is a circuit diagram according to a second embodiment of the present invention.

<Explanation of symbols on main parts of the drawings>

Q1: first transistor Q2: second transistor

Q3: third transistor V1: first power supply

V2: second power supply BI: bias applied stage

According to a feature of a power amplifier bias circuit for a mobile communication terminal according to the present invention for solving the above problems, a first transistor stage for feeding back a bias applied to the power amplifier of the mobile communication terminal, and the first transistor stage; A second transistor stage interlocked with each other to suppress bias variation, a first power supply unit supplying power to a collector of the first transistor stage and a base of the second transistor stage, and a second supply of power to a collector of the second transistor stage And a power supply unit and a bias applying stage for applying constant voltage bias by the first transistor stage and the second transistor stage to the power amplifier.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a circuit diagram illustrating a bias circuit for a mobile communication terminal according to a first embodiment of the present invention. The first transistor Q1 feeds back a bias applied to a power amplifier of the mobile communication terminal. A second transistor Q2 interlocked with the transistor Q1 to suppress bias variation, a first power supply V1 supplying power to the collector of the first transistor Q1 and the base of the second transistor Q2; And a second power supply V2 for supplying power to the collector of the second transistor, and a bias applying stage BI for applying a constant voltage bias to the power amplifier by the first transistor Q1 and the second transistor Q2. ), And a third transistor Q3 for applying a bias to the bias applying terminal BI to amplify the power of the signal.

The first power source supplies power through a resistor R1 that regulates current input to the first and second transistor stages.

The first transistor includes a current regulating resistor R2 at a base, and the bias applying terminal BI is connected to a voltage stabilizing resistor R3 connected to a ground of a circuit.

The operation of the power amplification bias circuit for a mobile communication terminal according to the first embodiment of the present invention configured as described above is as follows.

First, currents Ic3, Ic1, Ic2, and Ib2 increase in the circuit due to the temperature rise due to the operation of the third transistor Q3, and thus Vb2 decreases. When Vb2 is decreased, Ic2 of the second transistor Q2 is decreased, and as lc2 is decreased, IR2, Ic1, Ib3, and Ic3 are decreased. At this time, IR1 decreases, that is, Vb2 increases again, and when Vb2 increases, the bias circuit is returned to the operating state for the first time, and the increase and decrease is repeated. When a change in the voltage (hereinafter, Vb3) of the bias applying terminal BI that applies the bias to the base of the third transistor Q3 is observed, Vb increases and decreases and maintains a constant bias state. In addition, the resistor R3 is used to stabilize the voltage of Vb3 according to the increase and decrease of Vb2. Therefore, the voltage of Vb3 maintains a stable constant voltage bias state and supplies the stabilized bias to the third transistor Q3 that amplifies the power of the signal.

FIG. 2 is a circuit diagram illustrating a power amplification bias circuit for a mobile communication terminal according to a second embodiment of the present invention, and a description of a configuration overlapping with the first embodiment will be omitted in the drawings.

In the second embodiment, the first transistor Q1 of the first embodiment is electrically connected to the base and the collector, and serves as a diode, and the current adjusting resistor R4 is connected to the collector of the first transistor Q1. The resistor R5 is connected to the emitter of the second transistor Q2, and the resistor R2 is connected to the base of the first transistor Q1 and the resistor is connected to the emitter of the second transistor Q2. R5) is connected to the base of the third transistor Q3.

The operation of the power amplification bias circuit for a mobile communication terminal according to the second embodiment of the present invention configured as described above will be described with reference to FIG. 3. The current Ic3 is increased in the circuit due to the temperature rise according to the operation of the third transistor Q3. , IR4, Ic2, and Ib2 increase, and thus Vb2 decreases. When Vb2 is decreased, Ic2 of the second transistor Q2 is decreased, and as lc2 is decreased, IR2, IR4, IR5, Ib3, and Ic3 decrease. At this time, IR1 decreases, that is, Vb2 increases again, and when Vb2 increases, the bias circuit is returned to the operating state for the first time, and the increase and decrease is repeated. When the base voltage (hereinafter, Vb3) of the third transistor Q3 is changed, the increase and decrease of Vb2 occurs and a constant bias state is maintained. Therefore, the voltage of Vb3 maintains a stable constant voltage bias state and supplies the stabilized bias to the third transistor Q3 that amplifies the power of the signal.

The power amplification bias circuit for a mobile communication terminal configured as described above may further include a temperature compensation transistor or a current regulating resistor in order to compensate for the temperature rise caused by the operation of the power amplifier.

The power amplification bias circuit for a mobile communication terminal according to the present invention configured as described above constitutes a circuit for compensating for temperature rise or power fluctuation generated when amplifying the power of an external input signal, thereby stabilizing a bias applied to the power amplifier. By improving the linearity of the amplifier, it is possible to increase the reliability of the terminal.

Claims (5)

A first transistor stage for feeding back a bias applied to the power amplifier of the mobile communication terminal; A second transistor stage interlocked with the first transistor stage to suppress bias variation; A first power supply unit supplying power to the collector of the first transistor stage and the base of the second transistor stage; A second power supply unit supplying power to the collector of the second transistor stage; And a bias applying stage for applying constant voltage bias by the first transistor stage and the second transistor stage to a power amplifier. The method of claim 1, And the first power supply unit includes a resistor for adjusting a current input to the first and second transistor terminals. The method of claim 1, The first transistor stage is a power amplification bias circuit for a mobile communication terminal, characterized in that the current control resistor is included in the base. The method of claim 1, The bias applying stage is a power amplification bias circuit for a mobile communication terminal, characterized in that it comprises a resistor connected to ground to stabilize the bias voltage. The method of claim 1, And the first transistor stage includes a base and a collector connected to each other to operate as a diode.